#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<queue>
#include<vector>


using namespace std;

class Solution {
public:
    int dx[4] = { 1,-1,0,0 };
    int dy[4] = { 0,0,1,-1 };
    int numIslands(vector<vector<char>>& grid) {
        int m = grid.size(), n = grid[0].size();
        vector<vector<bool>> vis(m, vector<bool>(n, false));
        queue<pair<int, int>> q;
        int ret = 0;
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (vis[i][j] == false && grid[i][j] == '1')
                {
                    ret++;
                    q.push({ i,j });
                    vis[i][j] = true;
                    while (q.size())
                    {
                        auto [a, b] = q.front();
                        q.pop();

                        for (int z = 0; z < 4; z++)
                        {
                            int x = a + dx[z];
                            int y = b + dy[z];
                            if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == '1' && vis[x][y] == false)
                            {
                                q.push({ x,y });
                                vis[x][y] = true;
                            }
                        }
                    }
                }
            }
        }
        return ret;
    }
};